1. Field of the Invention
The present invention relates to a structure of a droplet jet apparatus and, more specifically, to drive electrodes each formed on an actuator used as an energy transducer used for the ejection of droplets.
2. Description of the Related Art
Various droplet ejecting devices or jet apparatus using energy transducers have heretofore been developed for various applications such as ink-jet printers and put to practical use. Electrothermal transducers, such as a heating element, and electromechanical transducers, such as a piezoelectric material, are used as energy transducers employed in such droplet jet apparatus. A droplet jet apparatus using piezoelectric material in general has an advantage because restrictions are less on available liquid to be heated and there is a wide range of choices of the liquid as compared with an apparatus using a heating element. However, various problems arise in such apparatus in that a droplet jet apparatus using a piezoelectric element or actuator used as an electromechanical transducer has a low degree of integration compared with an apparatus using an electrothermal transducer wherein a semiconductor manufacturing process can be applied and a size reduction in the droplet jet apparatus is required. In droplet jet apparatus using a piezoelectric body as an energy transducer, an actuator or piezoelectric element is used having mainly piezoelectric and electrostrictive transversal effects, which is a so-called unimorph piezoelectric element or bimorph piezoelectric element.
A droplet jet apparatus designed to bring a piezoelectric element or actuator used as an energy transducer into high integration has been disclosed in U.S. Pat. Nos. 4,879,568, 4,887,100, and 5,016,028.
In these devices, a small-sized droplet jet apparatus is used that has a plurality of grooves (channels) serving as liquid channels and pressure chambers. The pressure chambers are defined in a piezoelectric material subjected to polarization processing along its thickness direction in a high-integration rate. Drive electrodes are formed on both sides of each of the walls made of piezoelectric materials for separating the respective grooves (channels) from each other to produce any piezoelectric and electrostrictive effects. The produced effects make a transformation of a shear mode and produce a pressure change in each groove (channel), thereby ejecting or jetting desired droplets from respective nozzles of a nozzle plate provided in front of the droplet jet apparatus.
However, in the droplet jet apparatus having the structure disclosed in the above publications, a detailed description is hardly made as to the drive electrodes formed on both sides of each wall made of piezoelectric material. Accordingly, many problems arose as to the design of the droplet jet apparatus in practice. Thus, it was very problematic to put the above-type droplet jet apparatus having stable droplet ejection characteristics to practical use.